1. Field of the Invention
The present invention relaters to a pressure cooker and more specifically to a pressure release valve used in a pressure cooker.
2. Prior Art
FIG. 8 illustrates the essential elements of one type of today's typical pressure release valve, disassembled, used in a pressure cooker and installed in the lid of a pressure cooker.
This pressure release valve substantially comprises a holding knob 1, a body packing 2 which is inside a holding element 3 and is connected by the supporting pin 1A to the holding knob 1 at its upper end, a valve plunger 4 installed inside the body packing 2 by being suspended by the supporting pin 1A.
The valve plunger 4 is integrally comprised of an upper shank portion 4A, a beveled portion 4B formed at the lower end of the upper shank portion 4A, and a lower shank portion 4C extending downward from the beveled portion 4B. A coil spring 5 is provided around the upper shank portion 4A of the valve plunger 4 to surround the upper shank portion 4A, with its upper end contacting the inside top portion of the body packing 2 and its lower end contacting the upper surface of the beveled portion 4B of the valve plunger 4. The lower shank portion 4C of the valve plunger 4 is inserted into a pressure release tube 6 that is threadedly connected to the body packing 2 so that the external thread 6a formed on the outer surface of the pressure release tube 6 is threadedly connected to the internal thread 2a formed on the inner surface of the body packing 2. The holding element 3, which has thereon the holding knob 1 and therein the body packing 2, the valve plunger 4, the coil spring 5 and the pressure release tube 6, is mounted on the lid 100 of a pot of a pressure cooler when a cylindrical lock nut 7 is threadedly connected to the holding element 3 so that the internal thread 7a formed on the inner surface of the cylindrical lock nut 7 is screwed to the external thread 3a formed on the outer surface of the holding element 3, with the surrounding area of an installation hole formed in the lid of the pressure cooker being sandwiched by the flange 3A of the holding element 3 and the upper end 7A of he cylindrical lock nut 7.
In this structure of the conventional pressure release valve, the pressure produced during cooking is maintained at a preset level that is set by the spring force of the coil spring 5 and the weight of the valve plunger 4, so that cocking under high pressure can be continued. When the pressure inside the pod of the pressure cooker becomes higher than a preset level, the pressure or pressurized steam passes through the space between the outer surface of the lower shank portion 4C of the valve plunger 4 and the inner surface of the pressure release tube 6 and raises the beveled portion 4B of the valve plunger 4 and then discharged out of the body packing 2 via an pressure discharge opening 2A, thus preventing the pressure inside the pod from becoming too high and thus preventing explosion of the pressure cooker.
However, the space, which is between the outer surface of the lower shank portion 4C of the valve plunger 4 and the inner surface of the pressure release tube 6 and is to adjust the flow amount of the pressure or pressurized steam, is as small as few millimeters. Accordingly, water from the steam can accumulate in the space and also food particle produced during cooking can also be caught in such a small space, thus creating clogging in the pressure release path that could lead to an explosion. Furthermore, since the space since between the outer surface of the lower shank portion 4C of the valve plunger 4 and the inner surface of the pressure release tube 6 is so small, release of the pressure inside the pot that is done after cooling is completed takes time, and thus the pressure release valve cannot meet the demand of after-cooking quick pressure release. In addition, during cooking food being cooked can come in direct contact with the constituting elements such as the valve plunger 4, the pressure release tube 6 and the lock nut 7, which could become the reason for clogging as well.